The UW-FHCRC CFAR International Core strives to optimize efficiencies by leveraging diverse global HIV research projects, increasing collaborations and networking, mentoring new US and international investigators, optimizing infrastructure in international settings, and facilitating new research directions. During the past decades. International Core researchers have contributed substantive research to identify effective HIV interventions. In the new 5-year cycle, the International Core is poised to develop a new portfolio of collaborative implementation research that will translate efficacy research to implementation scale-up. The Core will foster synergies between ongoing NIH-supported HIV research projects, promote demonstration projects of interventions and facilitate training and mentorship to determine cost-effectiveness as interventions are implemented. Our specific aims are: AIM 1: To facilitate research to address cutting-edge global HIV issues. We will emphasize implementation science in pilot awards, and promote research on combination HIV prevention, chronic treatment, and vulnerable populations. We will establish a new sub-Core on Economic Evaluation, partnering with the Bill and Melinda Gates Foundation to determine sustainability and cost considerations for implementation. AIM 2: To strategically expand and leverage collaborations and research projects. We will extend collaborations from mature partners (Kenya, Peru) to new partners including regional neighbor countries; in addition, we will leverage activities of relevant UW DGH Centers (HAI, l-TECH, Global WACh) and Seattle global health organizations (BMGF, PATH) to facilitate research by CFAR investigators. We will provide infrastructure and co-develop training for international sites with other UW-FHCRC CFAR Cores, including SPRC, Biostatistics and AAlMS. We will support inter-CFAR initiatives: specifically, the Women and HIV and sub-Saharan Africa inter-CFAR collaborations. AIM 3: To sustain investment in new investigators and broaden the scope of international partnerships. We will provide support for trainees and join with the Developmental core to support a new Mentored International Investigator Award. We will provide mentoring workshops, and provide accessible mentorship to new international trainees. During the past 5 years, the International Core has realized appreciable return on investment in publications, grants, and new global HIV research leaders. We anticipate expanded relevance and efficiencies directly paralleling needs as the global HIV response transitions from emergent to sustainable strategies.